Automatic safety-stop for line-shafts.



C. D. SWETT.

Patented Dec. 5, 1916.

2 SHEETSSHEET 1.

APPLICATION FILED JUNE 6.1914.

AUTOMATIC SAFETY STOP FOR LINE SHAFTS.

IN V ICN'IOR C. D. SWETT.

AUTOMATIC SAFETY STOP FOR LINE SHAFTS.

APPLICATION FILED JUNE 6.19M.

Patented Dec. 5, 1916.

2 SHEEISSHEET 2.

GASWELL D. SWE'IT, 0F REDWOOD CITY, CALIFORNIA.

AUTOMATIC SAFETY-STOP FOR LINE-SHAFTS.

Specification of Letters Patent.

Patented Dec. 5, 1916.

Application filed .Tune 6, 1914. Serial No: 843,466.

To all whom it may concern Be it known that I, CAswELL D. SWETT, a' citizen of the United States, residing at Redwood City, in the county of San Mateo and State of California, have invented new and useful Improvements in Automatic Safety-Stops for Line-Shafts, of which the following is a specification.

This invention relates to means to overcome momentum of line-shafts and other machinery connected thereto and operable thereby, and to bring the mechanism to a stop as soon as possible, and pertains especially to mechanism for stopping line shafting operated from a single, double or threephase induction motor.

It is one of the objects of the present invention to provide means designed to prevent accidents in machinery where a. line shaft is employed to drive machinery, with the object of protecting the workmen against death or injury, and to prevent injury to the machinery.

It is a particular object of the present invention to provide an apparatus for the stop ping of rotation of a line-shaft when the latter is operated by power derived from electric motors; to provide in the apparatus the combination with the motor of an electric system, including a switch for supplying current to drive the motor in one direction, and which switch may be thrown to reverse the connection of the feed wires with the motor and thereby to reverse the direction of movement of the motor and check the momentum of the shafting so that in the event of an accident along the line of machinery operated by the line-shaft the revolution of the line-shaft may be brought to a stop as quickly as possible; and to provide means whereby, when the direction of the motor is reversed to overcome the momentum of the shafting and its moving parts, the current to the motor is automatically interrupted at the instant the shaft starts to reverse, so that the motor stops practically as soon as the lineshaft stops. In other words, the reversing of the direction of the motor quickens the stopping of the shafting and the stopping of the shafting stops the motor..

The invention consists of theparts and the construction and combination of parts as havlng reference to the accompanying drawr ings, in which Figure 1 is a View showing the motor and the. line-shaft driven thereby, with the wiring system shown diagrammatically. Fig. 2 is a side elevation, partlybroken away, of the automatic cut-out switch and its actuator. Fig. 3 is a transverse section through the line-shaft, showing the actuator partly in section and partly in end view and showing the automatic switch as latched in the circuit-closing position.

In Fig. 1, 2 represents an electric motor of suitabletype transmitting power by a driving belt or other suitable transmitting means to a pulley wheel 4, which is secured on a line-shaft 5 by which power may be distributed to various machine tools, or other mechanism, in a mill, machine shop, or other establishment. Connected to the motor are the service wires 6, 7 and 8, in this type representing a three-phase system in which 8 is the neutral wire. The wires 6 and 7 are secured in terminals 9 and 10 of a switch A, of suitable type, having binding posts 11 and 12, upon which are plvoted the switch blades 13 and 14. The switch blades are connected by a switch handle so as to be thrown from the terminals 9 and 10 to a reverse position at terminals 15 and 16 from which run respectively wires 15' and ,16'. Wire 16 is connected to the wire 6 of the motor circuit and the wire 15 is connected to the wire 7 of the motor circuit.

To the switch pivot terminals 11 and 12 are secured feed wires 19 and 20, which are connected to respective terminals '21 and 22,

' Fig. 2, of a switch 23, the knife blades 24 of which are pivoted upon terminals 25. To

the terminals 25 are separately connected feed wires 26 and 27. Thus, when the switch blades 24 are thrown into contact with the terminals 21 and 22 and circuit from the main feed wires 26 and 27 is closed to the switch terminals 12 and 11, and when the switch blades 13 and 14 are thrown into conshaft may be driven in any direction according to requirements, so long as the switch blades 24 are closing the circuit in the wires 26 and 27 ,and 19 and 20. Then if theoperator throws the switch blades 13-14vof the reversing switch to the opposite contact poles 15 and 16, the connection of the wires 19 and 20 will be reversed and consequently the operation of the motor will be checked.

In the event that an accident occurs in the mill or machine shop and it is desired to stop the motion of the line-shaft 5 in the least possible time, an operator or mechanic convenient to the reversing switch, of which any number may be provided, throws. this switch from the normal driving circuit-closing position to the reverse circuit-closing position to reverse the direction ofthe motor. It is desirable that, as soon as the reverse connection of the wires acts to retard the rotation of themotor and the momentum of the line-shaft 5 has been overcome, the motor be cut out so that the line-shaft will stop. For that purpose ll have provided means whereby the main switch 23 is automatically thrown open to break the circuit in the main feed wires at the instant the normal direction of rotation of the lineshaft 5 has been overcome and. at which it starts to reverse under the reversing operation of the motor.

The opening of the main switch 23 may be accomplished by suitable mechanism, here shown as including (Figs. 2 and 3), a spring 30, so positioned and of such a character as to react upon the switch blades 24 to tend to open the same about their pivot terminals 25. The switch opening tendency of the spring 30 is controlled and prevented when the switch is closed by gaf; latch or pawl 31, the nib or hook of which is adapted to engage an insulated plate 32 secured to the switch blades 24. The latch is pivoted at 33 upon a suitable bearing formed upon, or attached to',the switch 23, and is here shown as in the form of an angular lever, upon one end of which is mounted a cam roller 34, which, when thelatch 31 is engaging the. coacting plate 32 of the switch 23, rests upon a cam 35, of suitable peripheral contour, which in the present instance is formed upon or attached to a drum 36.

The cam drum 36 is loosely mounted upon present invention to provide means whereby the line shaft may revolve normally without affecting the switch releasing means, but which will operate, after the shaft has been brought to a stop and tends to rotate in a. reverse direction, to release the switch 23. For this purpose any suitable means may be used, the present ratchet and pawl being illustrative of a practical means.

I Assuming that an emergency requires the stopping of the line-shaft 5, an operator or mechanic will throw the reversing switch 15 from the direct driving positioncircuit to the reverse driving circuit by throwing in the wires 15 and 16 so as to reverse the direction of rotation of the motor, the energy of which will be transmitted by the belt to overcome the forward or normal drive of the line-shaft. As soon as the reversing tendency of the motor accomplishes the stopping ofthe line-shaft and the latter tends to reverse its rotation, then the ratchet wheel 38 would abut against the pawl 37 of the drum 36 and start to rotate this in the direction indicated by the dotted arrow a, Fig. 3, with the result that the cam 35 would lift the roller 34 of the releasing latch 31 and throw the latter to disengage the switch blades 24 of the switch 23, whereupon the operating spring 30 would react upon the switch blades to throw'them to open position and break the circuit through the feed wires 2627 and 1920.

As the main circuit to the motor is broken automatically, upon the initial reversing movement of the line-shaft 5 and the drum 36, when coupled thereto, the operation of the shaft and motor would quickly cease, owing to the fact that motion in the reverse direction of the line-shaft would have been so small as to produce but a negligible reverse momentum of the parts on the lineshaft. After the machinery has been stopped and it is desired to again start up, the reverse switch blades 1314 are thrown to neutral position or to closethe normal driving circuit of the motor 2, through the switch terminals 9 and 10 of the motor circuit wipes 6 and 7, and the operator may close the switch 23 by pulling on theswitch cord 39. which is connected to the handle of be drawn down to circuit-closing position. Upon the resumption of normal turning motion of the line-shaft 5 the cam drum 36 would be carried around with the same, owing to triction, until the cam roller seat passes again under and engages the roller 34, whereupon the resistance of the latter serves to overcome the tendency of rotation due to friction of the drum 36 with the shaft.

The main switch 23 includes a switch plate or base which is suitably mounted with relation to the line-shaft 5 and held in the switch blades 24, so that the latter can proper position by means of suitable hanger rods &0, depending from a convenient support. To the lower ends of the hanger rods 40 are secured pendent bracket hangers 41, upon which the switch base is mounted, the hangers" having journal boxes 42 through which the shaft 5 passes. Between the boxes 42 the coupling drum 36 is mounted. The coupling or cam drum is provided with a journal or hub portion 36 on one side and with a detachable face plateor head 36 on the opposite side for concealing and protecting the coupling mechanism within the drum.

Having thus described my invention, what I claim and desire to secure by Letters Patent is I 1. The combination of an electric motor, a motor circuit, a shaft operated from the motor, means for reversing the motor torque to hasten the stoppage of said shaft, a switch for controlling the normal motor circuit, means for holding said switch in closedposition and means for effectingthe opening of said switch simultaneously with the initial reverse movement of said shaft.

2. The combination of an electric'motor, a motor circuit, a shaft operated from the motor, means for reversing the motor torque to hasten the stoppage of said shaft, a selfopening switch for controlling the normal motor circuit, and means for retaining said switch in closed position and operated by the initial reverse movement of said shaft to permit the switch to open.

3. The combination of an electric motor, a motor circuit, a shaft operated from the motor, means for reversing the motor torque to hasten the stoppage of said shaft, a selfopening switch for controlling the motor circuit, and means for locking said switch in closed position and operated by the initial reverse movement of said shaft to permit the switch to open.

4. The combination of an electric motor,

a a shaft driven thereby, means for reversing the motor torque to hasten the stoppage of the shaft, a self-opening switch to control the motor circuit, a latch for holding said switch normally closed, and means carried by said shaft and-operable on an initial reverse movement. thereof to trip the latch and permit said switch to open.

' means 5. A safety control apparatus for lineshafting driven by a motor, comprising in combination with the motor and the shaft, amain feed wire system connected to the motor, a switch interposed in the feed wire system for reversing the direction of rotation of said motor and through it the shafting, a main switch between which and the, motor the reversing switch is interposed, for automatically opening the main switch, and a device for'locking the switch in closed position and controlled by the direction of rotation of the line-shaft for releasing the main switch so that the circuit to the motor is broken.

6. A safety control apparatus for lineing, a main switch between which and the motor the reversing switch is interposed,

means for automatically opening the main switch, a device for locking the switch in closed position and controlled by the direction of rotation of the line-shaft for releasing the inain switch so that the circuit to the motor is broken, and a controller mounted upon said shaft for holding said device in closed position during the rotation of the shaft in normal direction and operative to throw said device upon the rotation of said shaft in a reverse direction.

7. A safety control apparatus for lineshafting driven by a motor, comprising in combination withthe motor and the shaft, a main feed wire system connected to the motor, a switch interposed in the feedwire system for reversing the direction of rotation of said motor and through it the shafting, a main switch between which and the motor the reversing switch is interposed, means for automatically opening the main switch, a device for locking the switch in closed position and controlled by the direction of rotation of the line-shaft. for releasingthe main switch so that the circuit to the motor is broken, and a controller mounted upon said shaft for holding said device in closed position during the rotation of the shaft in normal direction and operative to throw said device upon the rotation of said shaft in a reverse direction, said means including a member loose upon said shaft, and a coupling instrumentality for positively engaging said means to the shaft when the latter is reversed.

8. The combination of a motor, a motor circuit, a shaft operated by the motor, a main switch, means for automatically opening the switch, means operated by the shaft to control the operation of the switch, said means comprising a cam loosely mounted upon the shaft whereby the latter may run freely in onedirection, a device for coupling verses its directionxof rotation, and a de-. vice for holding the switch in closed position and actuated by the cam to release the 'the shaft to said cam when the shaft resition to energize the motor, and a means controlling said trigger and adapted when said shaft rotates reverse to the normal to actuate said trigger to release the switch whereby the motor circuit will be broken.

10. The combination of a switch for closing an electric circuit, a motor, the circuit of which is closed by said switch, means for automatically opening the switch, a shaft adapted to be driven in either direction by said motor, means operative to hold the switch in closed position while the shaft is rotating normally and which will be actuated by the shaft when rotating reversely to mot/wee member and actuated thereby when the shaft is reversed.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

CASWELL D. SWETT.

Witnesses:

IRVINE SINNETT, W. W. HEALEY. 

